Why input values can't be updated ?

I was testing the PHP version of editor (v. 1.0) but I don't understand why I can't update the default HTML values in the editor. In fact the value is "re-writing" by the hidden field. And in the hidden field, we found the default value. So I can't change the value in the $_POST when I submit the form.

How can I do please

I amazing to see that the demo works great but not my script. Is it due to my version of PHP (4.1.2)